Refinements in air-quality protection and seal control, in a particulate-material gun usable with silica fume

摘要

Dust emission is controlled by a preferably short fill at the expulsion end of each chamber, and selective venting of residual pressure through the air-inlet end. This selective venting is accomplished through use of a novel seal or "pad" that has an extension for tightly covering and sealing the material-exhaust end of each chamber while the chamber is in a dust-control plenum. The pad extension is notched so that it leaves the air-inlet end uncovered, permitting pressure venting through the notch and the air-inlet end. To provide truly effective sealing of the pad extension against the wear plate above the chamber that is in the plenum, the extension is reinforced by a strong metal plate which is embedded in the pad. Careful contouring of the main material-conveying ports in the pad optimizes the performance. A new all-pneumatic pad-clamping pressure-control system has been found to provide excellent control of pressure and uniformity of wear, with a minimum of working parts and adjustments.